The present invention relates generally to fields of motion picture, television and other multi-media production. More particularly, the invention relates to methods for monitoring the amount of unexposed film remaining in a motion picture film magazine by recording film length data on a transparent magnetic recording layer contained on a motion picture film.
The typical configuration for motion picture cameras is to have a detachable film magazine with two separate film reels, one for unexposed film (supply reel) and one for exposed film (takeup reel). Such a film magazine has been described in U.S. Pat. Nos. 4,418,994 and 4,576,455, for example. Referring now to FIG. 1 of the prior art, film magazine 20 contains supply reel 23 and takeup reel 24. Film is conveyed from the supply reel 23 through the light trap block 30 into the interior of the motion picture camera 32. Alternatively, some pieces of equipment have separate magazines or cassettes, with again, one for unexposed film and one for exposed film. Referring now to FIG. 2 of the prior art, a motion picture camera 34, which for the purpose of illustration is depicted on tripod 35, has supply magazine 37 containing unexposed film and takeup magazine 36 containing exposed film attached to the body of the camera. The magazines depicted in FIGS. 1 and 2 are constructed in such a way to prevent light from exposing the film while it is in the magazine. An aperture exists that allows the end of the roll of film to protrude from the magazine and which allows additional film to be pulled from the roll in the magazine, or drawn into the magazine. Given the light-tight nature of the magazines, there is no direct way to observe the roll of film and specifically no direct way to determine the quantity of film in the supply chamber to assure that there is sufficient film available for a planned photographic event.
One method to infer the quantity of film in the supply magazine is to keep a written record, which is often kept on written labels on the front of the magazine, of the amount of film remaining in the magazine. For example, when the unexposed film is loaded into the magazine, a notation is made of the quantity of film that is placed in the magazine. During a photographic event, the amount of film being used can be determined by timing the duration of photography and multiplying that duration by the rate of film use by the camera or by consulting a counter on the camera or recording device that may be present to record film usage. The amount of film used is subtracted from the length of film known to exist in the magazine prior to photography and a new remaining length is recorded on the label or other record. This method is only as good as the fastidiousness of the record keeper, and there is no way, short of taking the magazine into a darkroom and opening the can and examining the roll by feel, to determine how much film is in the magazine.
Another method to infer the approximate quantity of film remaining in a magazine is to use a magazine which has a method for indicating the approximate diameter of the roll in the magazine, such as through the use of a spring loaded lever, one end of which contacts the outer diameter of the film roll as described in U.S. Pat. No. 4,418,994. The position of the level is transmitted to a dial or scale on the exterior of the magazine that can be viewed by the camera operator. The scale is calibrated to indicate the approximate length of the film remaining in the magazine. Referring again to FIG. 1. of the prior art, a calibrated stationary scale 26 fixed with respect to the magazine 20 cooperates with a pointer 28 attached to a spring loaded lever to provide a visual indication of the amount of film remaining on the supply reel 23. One disadvantage of this method is that all magazines are not equipped with this mechanism. Another is that it is only approximate. Finally, since this method relies on inferring the length of film from the diameter of the roll, the actual length is dependent on the thickness of the film and the diameter of the core on which it is wound, both of which can vary.
Motion picture films containing a magnetic recording stripe or a magnetic recording layer have been described. For example, U.S. Pat. Nos. 4,008,088 and 4,341,855 disclose a motion picture film containing a magnetic recording stripe for use in sound recording. However, the application of a magnetic recording stripe onto a photographic film is very undesirable from a manufacturing standpoint.
An innovation in data communication between different stages of film use and processing for motion picture film was introduced as described in the publication xe2x80x9cDATAKODE Magnetic Control Surfacexe2x80x9d by Eastman Kodak Company 1983 (Publication No. V3-517). A layer approximately 5 xcexcm thick containing magnetic oxide particles was coated across the entire back surface of a roll of motion picture film to provide the capability to magnetically record digital data on the film without interfering with normal photographic use of the film. It has been suggested that this permitted recording of different types of digital data at different stages of production of a motion picture which allowed for information exchange such as camera, lighting and filter data at the time of shooting to printer exposure control information in the laboratory to theater automation control signals during exhibition. There has been no suggestion, however, to employ such magnetic surface to monitoring the amount of unexposed film remaining in a motion picture film magazine.
More recently, it has been proposed to employ a virtually transparent magnetic layer on still photography filmstrip to allow for magnetic recording of data in one or more longitudinal tracks associated with individual film image frames for information exchange purposes as part of the recently introduced Advanced Photo System. An example of such a system is described in commonly assigned U.S. Pat. No. 4,965,627 issued Oct. 23, 1990. In order to provide quick access to particular data at any stage of film use, related data is preferably grouped and recorded in specific predetermined tracks. Camera data is recorded in several dedicated longitudinal tracks located along the filmstrip edges. The data is preferably recorded in pulse position encoded form in order to be largely independent of film transport velocity.
There has also been proposed, recently, still photography camera systems that allow for removal of a film roll before all available film frames have been exposed, and later insertion in the same or different camera for exposure of the remaining film frames without double exposure of the previously exposed frames. This feature is generally referred to as xe2x80x9cMid-Roll Interruptxe2x80x9d (or MRI) or xe2x80x9cMid-Roll Changexe2x80x9d (or MRC). While a number of arrangements have been proposed for implementing this feature, one that is generally accepted involves detecting the existence of magnetically recorded data adjacent exposed frames during loading of the film into the camera to position the film at the next available unexposed frame as indicated by the absence of recorded data. In less expensive MRC-equipped cameras it is necessary only to detect the existence of recorded data without decoding the detected data to implement the MRC function. In more sophisticated cameras, it may also be required that the data be decoded for transfer of operating control information to the camera controller while at the same time serving as an indicator of exposed frame positions. Representative patents which disclose MRC camera features for use with films having a magnetic recording layer include U.S. Pat. Nos. 5,006,873, 5,477,289, and 5,519,462. While one function of such still photography systems is to distinguish between exposed and unexposed areas on a film strip, there is no disclosure relating to monitoring the amount of unexposed film remaining in a motion picture film magazine.
U.S. Pat. No. 5,737,650 describes a photographic medium cartridge with a magnetically activated status indicator. The status indicator is designed to provide information, through interaction with a magnetic member carried on a photographic filmstrip, as to whether the filmstrip has been properly loaded into a camera, whether the filmstrip in the cartridge is exposed or unexposed, and the number of exposures made or remaining to be made on the filmstrip in the cartridge.
It is a general aim of the present invention to provide an improved method for easily and accurately determining and indicating the amount of unexposed photographic film remaining in a motion picture film magazine.
In accordance with the present invention there is provided a method for monitoring the amount of unexposed photographic film remaining in a motion picture camera film magazine that includes the steps of: providing an unexposed motion picture film containing a support having at least one light sensitive image recording layer and a transparent magnetic recording layer; recording film length data on the transparent magnetic recording layer of the unexposed motion picture film; loading the unexposed motion picture film in a motion picture film magazine; and reading the film length data from the transparent magnetic recording layer as it is removed from the film supply magazine to provide an indication of the amount of unexposed film remaining in the motion picture film magazine. The amount of unexposed film remaining may be displayed in a read-out device associated with the film magazine or camera.